cmd/golangorg: remove go-source meta tag for golang.org/x repos

The go-source meta tag was added in CL 2719 so that godoc.org could
link to source code for golang.org/x repos. godoc.org is now served
by golang.org/x/pkgsite rather than by github.com/golang/gddo, and
x/pkgsite maintains this mapping for golang.org/x repos itself in
x/pkgsite/internal/source. Drop the tag since it has become unused
and stale (we've since switched to https://cs.opensource.google/go
for viewing x/ repo source code).

Updates golang/go#40477.

Change-Id: Id029e58bfdb838e040241d6bf7677349cec6e04a
Reviewed-on: https://go-review.googlesource.com/c/website/+/484515
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/cmd/golangorg/server.go b/cmd/golangorg/server.go
index 488e838..1fb1a7c 100644
--- a/cmd/golangorg/server.go
+++ b/cmd/golangorg/server.go
@@ -578,7 +578,6 @@
 <title>The Go Programming Language</title>
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
 <meta name="go-import" content="golang.org/x/{{.Proj}} git https://go.googlesource.com/{{.Proj}}">
-<meta name="go-source" content="golang.org/x/{{.Proj}} https://github.com/golang/{{.Proj}}/ https://github.com/golang/{{.Proj}}/tree/master{/dir} https://github.com/golang/{{.Proj}}/blob/master{/dir}/{file}#L{line}">
 <meta http-equiv="refresh" content="0; url=https://pkg.go.dev/golang.org/x/{{.Proj}}{{.Suffix}}">
 </head>
 <body>